The failure of a significant number of tumors to respond to drug and/or radiation therapy is a serious problem in the treatment of cancer. In fact, this is one of the main reasons why many of the most prevalent forms of human cancer still resist effective chemotherapeutic intervention, despite certain advances in the field of chemotherapy.
Cancer is now primarily treated with one or a combination of three types of therapies: surgery, radiation, and chemotherapy. Surgery is a traditional approach in which all or part of a tumor is removed from the body. Surgery generally is only effective for treating the earlier stages of cancer. While surgery is sometimes effective in removing tumors located at certain sites, for example, in the breast, colon, and skin, it cannot be used in the treatment of tumors located in other areas, inaccessible to surgeons, nor in the treatment of disseminated neoplastic conditions such as leukemia. For more than 50% of cancer individuals, by the time they are diagnosed they are no longer candidates for effective surgical treatment. Surgical procedures may increase tumor metastases through blood circulation during surgery. Most of cancer individuals do not die from the cancer at the time of diagnosis or surgery, but rather die from the metastasis and the recurrence of the cancer.
Other therapies are also often ineffective. Radiation therapy is only effective for individuals who present with clinically localized disease at early and middle stages of cancer, and is not effective for the late stages of cancer with metastasis. Radiation is generally applied to a defined area of the subject's body which contains abnormal proliferative tissue, in order to maximize the dose absorbed by the abnormal tissue and minimize the dose absorbed by the nearby normal tissue. However, it is difficult (if not impossible) to selectively administer therapeutic radiation to the abnormal tissue. Thus, normal tissue proximate to the abnormal tissue is also exposed to potentially damaging doses of radiation throughout the course of treatment. There are also some treatments that require exposure of the subject's entire body to the radiation, in a procedure called “total body irradiation”, or “TBI.” The efficacy of radiotherapeutic techniques in destroying abnormal proliferative cells is therefore balanced by associated cytotoxic effects on nearby normal cells. Because of this, radiotherapy techniques have an inherently narrow therapeutic index which results in the inadequate treatment of most tumors. Even the best radiotherapeutic techniques may result in incomplete tumor reduction, tumor recurrence, increasing tumor burden, and induction of radiation resistant tumors.
Chemotherapy involves the disruption of cell replication or cell metabolism. Chemotherapy can be effective, but there are severe side effects, e.g., vomiting, low white blood cells (WBC), loss of hair, loss of weight and other toxic effects. Because of the extremely toxic side effects, many cancer individuals cannot successfully finish a complete chemotherapy regime. Chemotherapy-induced side effects significantly impact the quality of life of the individual and may dramatically influence individual compliance with treatment. Additionally, adverse side effects associated with chemotherapeutic agents are generally the major dose-limiting toxicity (DLT) in the administration of these drugs. For example, mucositis is one of the major dose limiting toxicity for several anticancer agents, including the antimetabolite cytotoxic agents 5-FU, methotrexate, and antitumor antibiotics, such as doxorubicin. Many of these chemotherapy-induced side effects if severe may lead to hospitalization, or require treatment with analgesics for the treatment of pain. Some cancer individuals die from the chemotherapy due to poor tolerance to the chemotherapy. The extreme side effects of anticancer drugs are caused by the poor target specificity of such drugs. The drugs circulate through most normal organs of individuals as well as intended target tumors. The poor target specificity that causes side effects also decreases the efficacy of chemotherapy because only a fraction of the drugs is correctly targeted. The efficacy of chemotherapy is further decreased by poor retention of the anti-cancer drugs within the target tumors.
Due to the severity and breadth of neoplasm, tumor and cancer, there is a great need for effective treatments of such diseases or disorders that overcome the shortcomings of surgery, chemotherapy, and radiation treatment.
Problems of Chemotherapeutic Agents
The drug resistance problem is a reason for the added importance of combination chemotherapy, as the therapy both has to avoid the emergence of resistant cells and to kill pre-existing cells which are already drug resistant.
Drug resistance is the name given to the circumstance when a disease does not respond to a treatment drug or drugs. Drug resistance can be either intrinsic, which means the disease has never been responsive to the drug or drugs, or it can be acquired, which means the disease ceases responding to a drug or drugs that the disease had previously been responsive to. Multidrug resistance (MDR) is a specific type of drug resistance that is characterized by cross-resistance of a disease to more than one functionally and/or structurally unrelated drugs. Multidrug resistance in the field of cancer is discussed in greater detail in “Detoxification Mechanisms and Tumor Cell Resistance to Anticancer Drugs,” by Kuzmich and Tew, particularly section VII “The Multidrug-Resistant Phenotype (MDR),” Medical Research Reviews, Vol. 11, No. 2, 185-217, (Section VII is at pp. 208-213) (1991); and in “Multidrug Resistance and Chemosensitization: Therapeutic Implications for Cancer Chemotherapy,” by Georges, Sharom and Ling, Advances in Pharmacology, Vol. 21, 185-220 (1990).
One form of multi-drug resistance (MDR) is mediated by a membrane bound 170-180 kD energy-dependent efflux pump designated as P-glycoprotein (P-gp). P-glycoprotein has been shown to play a major role in the intrinsic and acquired resistance of a number of human tumors against hydrophobic, natural product drugs. Drugs that act as substrates for and are consequently detoxified by P-gp include the vinca alkaloids (vincristine and vinblastine), anthracyclines (Adriamycin), and epipodophyllotoxins (etoposide). While P-gp associated MDR is a major determinant in tumor cell resistance to chemotherapeutic agents, it is clear that the phenomenon of MDR is multifactorial and involves a number of different mechanisms.
A major complication of cancer chemotherapy and of antiviral chemotherapy is damage to bone marrow cells or suppression of their function. Specifically, chemotherapy damages or destroys hematopoietic precursor cells, primarily found in the bone marrow and spleen, impairing the production of new blood cells (granulocytes, lymphocytes, erythrocytes, monocytes, platelets, etc.). Treatment of cancer individuals with 5-fluorouracil, for example, reduces the number of leukocytes (lymphocytes and/or granulocytes), and can result in enhanced susceptibility of the individuals to infection. Many cancer individuals die of infection or other consequences of hematopoietic failure subsequent to chemotherapy. Chemotherapeutic agents can also result in subnormal formation of platelets which produces a propensity toward hemorrhage. Inhibition of erythrocyte production can result in anemia. For some cancer individuals, the risk of damage to the hematopoietic system or other important tissues frequently limits the opportunity for chemotherapy dose escalation of chemotherapy agents high enough to provide good antitumor or antiviral efficacy. Repeated or high dose cycles of chemotherapy may be responsible for severe stem cell depletion leading to serious long-term hematopoietic sequelea and marrow exhaustion.
Prevention of, or protection from, the side effects of chemotherapy would be a great benefit to cancer individuals. For life-threatening side effects, efforts have concentrated on altering the dose and schedules of the chemotherapeutic agent to reduce the side effects. Other options are becoming available, such as the use of granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage-CSF (GM-CSF), epidermal growth factor (EGF), interleukin 11, erythropoietin, thrombopoietin, megakaryocyte development and growth factor, pixykines, stem cell factor, FLT-ligand, as well as interleukins 1, 3, 6, and 7, to increase the number of normal cells in various tissues before the start of chemotherapy (See Jimenez and Yunis, Cancer Research 52:413-415; 1992). The mechanisms of protection by these factors, while not fully understood, are most likely associated with an increase in the number of normal critical target cells before treatment with cytotoxic agents, and not with increased survival of cells following chemotherapy.
Chemotherapeutic Targeting For Tumor Treatment
Both the growth and metastasis of solid tumors are angiogenesis-dependent (Folkman, J. Cancer Res., 46, 467-73 (1986); Folkman, J. Nat. Cancer Inst., 82, 4-6 (1989); Folkman et al., “Tumor Angiogenesis,” Chapter 10, pp. 206-32, in The Molecular Basis of Cancer, Mendelsohn et al., eds. (W. B. Saunders, 1995)). It has been shown, for example, that tumors which enlarge to greater than 2 mm in diameter must obtain their own blood supply and do so by inducing the growth of new capillary blood vessels. After these new blood vessels become embedded in the tumor, they provide nutrients and growth factors essential for tumor growth as well as a means for tumor cells to enter the circulation and metastasize to distant sites, such as liver, lung or bone (Weidner, New Eng. J. Med., 324(1), 1-8 (1991)). When used as drugs in tumor-bearing animals, natural inhibitors of angiogenesis can prevent the growth of small tumors (O'Reilly et al., O'Reilly et al., Cell, 79, 315-28 (1994)). Indeed, in some protocols, the application of such inhibitors leads to tumor regression and dormancy even after cessation of treatment (O'Reilly et al., Cell, 88, 277-85 (1997)). Moreover, supplying inhibitors of angiogenesis to certain tumors can potentiate their response to other therapeutic regimes (e.g., chemotherapy) (see, e.g., Teischer et al., Int. J. Cancer, 57, 920-25 (1994)).
Protein tyrosine kinases catalyze the phosphorylation of specific tyrosyl residues in various proteins involved in the regulation of cell growth and differentiation (A. F. Wilks, Progress in Growth Factor Research, 1990, 2, 97-111; S. A. Courtneidge, Dev. Supp. 1, 1993, 57-64; J. A. Cooper, Semin. Cell Biol., 1994, 5(6), 377-387; R. F. Paulson, Semin. Immunol., 1995, 7(4), 267-277; A. C. Chan, Curr. Opin. Immunol., 1996, 8(3), 394-401). Protein tyrosine kinases can be broadly classified as receptor (e.g. EGFr, c-erbB-2, c-met, tie-2, PDGFr, FGFr) or non-receptor (e.g. c-src, Ick, Zap70) kinases. Inappropriate or uncontrolled activation of many of these kinases, i.e. aberrant protein tyrosine kinase activity, for example by over-expression or mutation, has been shown to result in uncontrolled cell growth. For example, elevated epidermal growth factor receptor (EGFR) activity has been implicated in non-small cell lung, bladder and head and neck cancers, and increased c-erbB-2 activity in breast, ovarian, gastric and pancreatic cancers. Thus, inhibition of protein tyrosine kinases should be useful as a treatment for tumors such as those outlined above.
Growth factors are substances that induce cell proliferation, typically by binding to specific receptors on cell surfaces. Epidermal growth factor (EGF) induces proliferation of a variety of cells in vivo, and is required for the growth of most cultured cells. The EGF receptor is a 170-180 kD membrane-spanning glycoprotein, which is detectable on a wide variety of cell types. The extracellular N-terminal domain of the receptor is highly glycosylated and binds EGF antibodies that selectively bind to EGFR. Agents that competitively bind to EGFR have been used to treat certain types of cancer, since many tumors of mesodermal and ectodermal origin overexpress the EGF receptor. For example, the EGF receptor has been shown to be overexpressed in many gliomas, squamous cell carcinomas, breast carcinomas, melanomas, invasive bladder carcinomas and esophageal cancers. Attempts to exploit the EGFR system for anti-tumor therapy have generally involved the use of monoclonal antibodies against the EGFR. In addition, studies with primary human mammary tumors have shown a correlation between high EGFR expression and the presence of metastases, higher rates of proliferation, and shorter individual survival.
Herlyn et al., in U.S. Pat. No. 5,470,571, disclose the use of radiolabeled Mab 425 for treating gliomas that express EGFR. Herlyn et al. report that anti-EGFR antibodies may either stimulate or inhibit cancer cell growth and proliferation. Other monoclonal antibodies having specificity for EGFR, either alone or conjugated to a cytotoxic compound, have been reported as being effective for treating certain types of cancer. Bendig et al, in U.S. Pat. No. 5,558,864, disclose therapeutic anti-EGFR Mab's for competitively binding to EGFR. Heimbrook et al., in U.S. Pat. No. 5,690,928, disclose the use of EGF fused to a Pseudomonas species-derived endotoxin for the treatment of bladder cancer. Brown et al., in U.S. Pat. No. 5,859,018, disclose a method for treating diseases characterized by cellular hyperproliferation mediated by, inter alia, EGF.
Chemotherapeutic Modes of Administration
People diagnosed as having cancer are frequently treated with single or multiple chemotherapeutic agents to kill cancer cells at the primary tumor site or at distant sites to where cancer has metastasized. Chemotherapy treatment is typically given either in a single or in several large doses or over variable times of weeks to months. However, repeated or high dose cycles of chemotherapy may be responsible for increased toxicities and severe side effects.
New studies suggest that metronomic chemotherapy, the low-dose and frequent administration of cytotoxic agents without prolonged drug-free breaks, targets activated endothelial cells in the tumor vasculature. A number of preclinical studies have demonstrated superior anti-tumor efficacy, potent antiangiogenic effects, and reduced toxicity and side effects (e.g., myelosuppression) of metronomic regimes compared to maximum tolerated dose (MTD) counterparts (Bocci, et al., Cancer Res, 62:6938-6943, (2002); Bocci, et al., PNAS, vol, 100(22):12917-12922, (2003); and Bertolini, et al., Cancer Res, 63(15):4342-4346, (2003)). It remains unclear whether all chemotherapeutic drugs exert similar effects or whether some are better suited for such regimes than others. Nevertheless, metronomic chemotherapy appears to be effective in overcoming some of the major shortcomings associated with chemotherapy.
Chemotherapeutic Agents
Paclitaxel has been shown to have significant antineoplastic and anticancer effects in drug-refractory ovarian cancer and has shown excellent antitumor activity in a wide variety of tumor models, and also inhibits angiogenesis when used at very low doses (Grant et al., Int. J. Cancer, 2003). The poor aqueous solubility of paclitaxel, however, presents a problem for human administration. Indeed, the delivery of drugs that are inherently insoluble or poorly soluble in an aqueous medium can be seriously impaired if oral delivery is not effective. Accordingly, currently used paclitaxel formulations (e.g., Taxol®) require a Cremophor® to solubilize the drug. The presence of Cremophor® in this formulation has been linked to severe hypersensitivity reactions in animals (Lorenz et al., Agents Actions 7:63-67 (1987)) and humans (Weiss et al., J. Clin. Oncol. 8:1263-68 (1990)) and consequently requires premedication of individuals with corticosteroids (dexamethasone) and antihistamines. It was also reported that clinically relevant concentrations of the formulation vehicle Cremophor® EL in Taxol® nullify the antiangiogenic activity of paclitaxel, suggesting that this agent or other anticancer drugs formulated in Cremophor® EL may need to be used at much higher doses than anticipated to achieve effective metronomic chemotherapy (Ng et al., Cancer Res., 64:821-824 (2004)). As such, the advantage of the lack of undesirable side effects associated with low-dose paclitaxel regimes vs. conventional MTD chemotherapy may be compromised. See also U.S. Patent Pub. No. 2004/0143004; WO00/64437.
Abraxane® is a Cremophor® EL-Free Nanoparticle Albumin-Bound Paclitaxel
Preclinical models have shown significant improvement in the safety and efficacy of Abraxane® compared with Taxol® (Desai et al., EORTC-NCI-AACR, 2004) and in individuals with metastatic breast cancer (O'Shaughnessy et al., San Antonio Breast Cancer Symposium, Abstract #1122, December 2003). This is possibly due to the absence of surfactants (e.g., Cremophor® or Tween® 80, used in Taxol® and Taxotere®, respectively) in Abraxane®, and/or preferential utilization of an albumin-based transport mechanism utilizing gp60/caveolae on microvascular endothelial cells (Desai et al., EORTC-NCI-AACR, 2004). In addition, both Cremophor® and Tween® 80 have been shown to strongly inhibit the binding of paclitaxel to albumin, possibly affecting albumin based transport (Desai et al., EORTC-NCI-AACR, 2004).
IDN5109 (Ortataxel) is a new taxane, currently in phase II, selected for its lack of cross-resistance in tumor cell lines expressing the multidrug resistant phenotype (MDR/Pgp) and inhibition of P-glycoprotein (Pgp) (Minderman; Cancer Chemother. Pharmacol. 2004; 53:363-9). Due to its hydrophobicity, IDN5109 is currently formulated in the surfactant Tween® 80 (same vehicle as Taxotere®). Removal of surfactants from taxane formulations e.g., in the case of nanoparticle albumin-bound paclitaxel (Abraxane®) showed improvements in safety and efficacy over their surfactant containing counterparts (O'Shaughnessy et al., San Antonio Breast Cancer Symposium, Abstract #1122, December 2003). Tween® 80 also strongly inhibited the binding of the taxane, paclitaxel, to albumin, possibly compromising albumin based drug transport via the gp60 receptor on microvessel endothelial cells (Desai et al., EORTC-NCI-AACR, 2004).
The antitumor activity of colchicine, which is the major alkaloid of the autumn crocus, Colchicum autumnale, and the African climbing lily, Gloriosa superba, was first reported at the beginning of the 20th century. The elucidation of its structure was finally completed from X-ray studies and a number of total syntheses (see Shiau et al., J. Pharm. Sci. 1978, 67(3) 394-397). Colchicine is thought to be a mitotic poison, particularly in tyhmic, intestinal, and hermatopoietic cells, which acts as a spindle poison and blocks the kinesis. Its effect on the mitotic spindle is thought to represent a special case of its effects on various organized, labile, fibrillar systems concerned with structure and movement.
Thiocolchicine dimer IDN5404 was selected for its activity in human ovarian subline resistant to cisplatin and topotecan A2780-CIS and A2780-TOP. This effect was related to dual mechanisms of action, i.e., microtubule activity as in Vinca alkaloids and a topoisomerase I inhibitory effect different from camptothecin. (Raspaglio, Biochemical Pharmacology 69:113-121 (2005)).
It has been found that nanoparticle compositions of a taxane (such as albumin bound paclitaxel (Abraxane®)) have significantly lower toxicities than other taxanes like Taxol® and Taxotere® with significantly improved outcomes in both safety and efficacy.
Combination chemotherapy, e.g., combining one or more chemotherapeutic agents or other modes of treatment, e.g., combining for example, chemotherapy with radiation or surgery and chemotherapy, have been found to be more successful than single agent chemotherapeutics or individual modes of treatment respectively.
Other references include U.S. Pub. No. 2006/0013819; U.S. Pub. No. 2006/0003931; WO05/117986; WO05/117978; and WO05/000900.
More effective treatments for proliferative diseases, especially cancer, are needed.
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